CA1294031C - Device for seismic exploration - Google Patents
Device for seismic explorationInfo
- Publication number
- CA1294031C CA1294031C CA000611728A CA611728A CA1294031C CA 1294031 C CA1294031 C CA 1294031C CA 000611728 A CA000611728 A CA 000611728A CA 611728 A CA611728 A CA 611728A CA 1294031 C CA1294031 C CA 1294031C
- Authority
- CA
- Canada
- Prior art keywords
- main cable
- geophones
- cable
- breaking strength
- geophone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
- G01V1/20—Arrangements of receiving elements, e.g. geophone pattern
- G01V1/201—Constructional details of seismic cables, e.g. streamers
Landscapes
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- Remote Sensing (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Geophysics And Detection Of Objects (AREA)
- Control Of Vending Devices And Auxiliary Devices For Vending Devices (AREA)
Abstract
ABSTRACT
A device for seismic exploration in the form of a towed streamer. The streamer is easily managed, is very flex-ible and has a low weight so that it may be towed with moderate tractive forces. It consists of a cable with an inner core (11), one or more layers(12)of insulated conductor pairs and an outer low-friction protective coating(13), and is characterised by the employment in both the core as well as in the outer low-friction protective layer of an acoustically almost inert mate-rial of low specific gravity. The seismic signals are obtained by means of series connected gimbal-mounted geophones.
A device for seismic exploration in the form of a towed streamer. The streamer is easily managed, is very flex-ible and has a low weight so that it may be towed with moderate tractive forces. It consists of a cable with an inner core (11), one or more layers(12)of insulated conductor pairs and an outer low-friction protective coating(13), and is characterised by the employment in both the core as well as in the outer low-friction protective layer of an acoustically almost inert mate-rial of low specific gravity. The seismic signals are obtained by means of series connected gimbal-mounted geophones.
Description
The invention concerns a device for seismic exploration specially designed for ice- and snow-covered regions, but also applicable on other surfaces on land or on the sea-bed.
Until now land-based prospecting techniques have been very labour intensive and time-consuming, and have not had the functional or economic efficiency which is at present avail-able for marine seismic surveying.
Several suggestions have therefore been made for improve-ments of land-based seismic operations/ for example the use of a towed main cable (streamer) to which subsidiary cables with automatically adjustable receiving instruments (geophones) are attached at suitable intervals. In order to use such towed systems on a solid surface it has until now been considered important that the cable system be able to withstand severe stresses and be so thick and strong that it can be towed within the area of operation. In snow-and ice-covered regions one has the additional risk that the cable may sink into the snow- and ice-cover and freeze in and thus increasing the strength/stress requirements.
Such a streamer system designed ~or use on snow and ice surfaces is known from US Patent No. 3,954,154 Bedenbender et al. Furthermore a method for mechanised land prospecting using the known streamer is known from US Patent No 3,923,121 Bedenbender et al.
The streamer has a main cable composed of individual sec-tions linked by means of connectors. A number of side strings with individual geophones are connected to the main ' l~a~
cable with the geophones interconnected within the main cable. A tensile core consisting of 7 steel wires is ar-ranged in the central region of the cable in order to with-stand a force of minimum 8 tons (16000 lbs). me steel core alone will thus have a diameter of at least 12 mm, and the resulting cable with surrounding rubber coating, conductor pairs, covering foils and outer mantle will weigh several kilograms per meter and have a substantial diameter of 40-60 mm or more. A streamer using such a cable will be very heavy and can be stiff and unmanageable, like a heavy steel hawser, and is therefore not weel-suited for use in arctic regions. In addition the steel wires will be acoustically active and possibly impair the signal quality. me construc-tions is therefore not suitable for fullscale commercial seismics, and in the above-mentioned patent No., informa-tion is forthcoming on how the streamer concept has behaved in practical trials, or on results achieved.
Thus it is the main object of the invention to develop an easily managed, towable device giving faster and cheaper data collection without adversely affecting the quality of the received signals and giving results as good as or better than those obtainable by conventional techniques.
, It is a further object of the invention to create a streamer which is essentially acoustically inert and does not reduce the quality of the signals recorded by the geophones and receiving instruments.
Yet another object of the invention is to produce a streamer which behaves like a flexible rope, is lightweight and floats upon or glides over the surface with low friction, which is easy to pull and which can serve a large number of geophones. In addition it has the object of preventing the freezing in place of the streamer during halts of some duration and of providing easy re~tarting even if the stre-amer is covered by snow or similar material.
:
3~
These objects are achieved accordiny to the invention by means of an apparatus for seismic exploration to be towed on a land surface and suitable for use on ice/snow surfaces, said apparatus comprising: a towable main cable comprising a plurality of linked cable sections each formed by a core capable of absorbing the stress of towing, at least one layer surrounding said core and formed of insulated conductor pairs of electrically conductive material for the transmission of received signals, and a sheath surrounding and protecting sald at least one layer of conductor 10 pairs, a plurality of geophone strings connected to said main cable at positions spaced longitudinally thereof, each said geophone string having spaced therealong a plurality of geophones electrically connected to said main cable, each said geophone string being capable of being aligned to extend outwardly in varying directions from said main cable with said plurality of geophones of each said geophone string bein~ located at different distances from said main cable; said core and said sheath each being formed of acoustically substantially inert material sufficient to substantially not interfere with seismic signals received by said geophones and transmitted to and by said at least one layer of conductor pairs; and said main cable having an outer diameter of less than 25 mm and a weight of less than 500 g per meter; whereby said main cable wi~h geophone strings connected thereto has a de~ree of flexibility and ease of handling sufficient to enable the same to be wound or coiled in the manner A
3~
26625-g6 of a rope and t~ glide over a ground surface under extreme temperature conditions.
The invention itself will now be described in more detail with references to the attached drawings where:
Fig. 1 shows the end section of the streamer with a towin~ arrangement, Fiy. 2 shows active section~ of the main cable of the streamer with atta~hed subsidiary cables, Fig. 3 shows a cross~section of the main cable, Fig. 4 shows a single auxiliary cable or geophone string, Fig. 5 shows a test line using conventional techniques and ordinary geophones, Fig. 6 shows a corresponding test line using th~
procedure in the invention and employing the streamer.
The main components in the operative device for seismic exploration are a streamer comprising a towing device, active sections and geophone ~trings.
The whole system (Fig. 1) is towed by a terrain vehicle 1 which also contains recording units and associated equipment.
Duriny start and while moving, the tractive force 3a 3~a being used at any time is measured by a strain-gauge 2 and the result shown on a display device in the cabin. Between the strain-gauge 2 and an acoustically inert tow~rope 4 is a safety wire 3 with a breaking strength of about 1.2 tons.
The active sections 6 are pulled by the tow-rope, while the seismic signal~ are transmitted to the recording units by a slack extension cable 5.
The snow-streamer itself (Fig. 2) is a cable 7 consisting of several units or sections - for example 6 units of 250 m. The units are connected by means of quick-release con-nectors 8. A number of auxiliary cables or geophone strings 9 are attached to the cable each carrying a number of re-ceiving instruments or geophones. The geophones are series connected outside the main cabl~, thus reducing the stiff-ness and diameter of the main cable.
The cable 7 is in sections in order to:
- spread the elongation due to stretching during operations ~ver several sections, - facilitate assembly~disassembly, mobilisation/-demobilisation - enable the replacement and repair of defective components while operations are in progress.
The cable 7 (Fig. 3) has at its centre a tension member 11 of acoustically almost inert material which is flexible and of low density, then three layPrs 12 of plastic insu-lated conductor pairs of copper for signal transmission.
The tension member has a diameter of 6.9 mm and a breaking strength of 3000 kg. Kevlar ~ , a synthetic aromatic poly-amide fibre with a specific gravity of 1.15 produced by Du Pont is employed as the fibre material. Externally the cable is covered by low-friction protective coating 13 of elasto-mer material, an acoustically almost inert material with great flexibility and low friction. The main cable has a diameter of 19.2 mm and the weight is 400 g per meter. The .
~L2~ 3~
breaking strenght of the tensile element (core) can there-fore be as low as 3 tons for a 1500 m cable which is to be used in show/ice covered areas. A thin metal coated plastic foil 14 is placed between the conductor pairs 12 and the low-friction protective coating 13.
The low-friction protective coa~ing is coloured off-white in order to avoid the risk that halts of some duration should lead to melting and later refreezing of snow/ice next to the cable. The protective coating has a thickness of 2.6 mm and is guaranteed for temperatures between -51 C and +107~C. It is ~lexible and slips easily over all solid surfaces. The lowfriction protective coating is made of Hytrel ~ a thermoplastic polyester wi~h specific gravity 1.24 produced by Du Pont.
The seismic signals are obtained by means of receiving instruments (geophones~ which are moulded into the auxiliary cables (geophone strings) 9 at fixed intervals (Fig. 4~.
The receiving instruments 10 are series connected outside the main cable so that each geophone string comprises a group (antenna) of for example 25 m length. Each group has 6 or more receiving instruments 10. With an average dis-tance between connecting points of 25 m there are 60 seismic channels on a streamer which is 1500 m long, so that with 6 instruments per group there are 360 instruments. The receiving instruments 10 are hal~-gimballed, that is to say they always lie in a vertical plane coinciding with the direction of the geophone string.
At the points of attachment between the geophone strings 9 and the main cable 7 the breaking strength is 250 kg, while the breaking strength between individual instruments 10 in the geophone strings 9 is 85 kg. These specifications are chosen in order to obtain controlled breaking in the event of jamming of a receiving device 10 in the surface.
~2~
The whole system is waterproof and may be towed as a bottom cable. It is flexible in use and may be towed as one long unit or as several units in freely chosen geometric con-figurations. The system has been tested on ice/snow sur-faces, but can owing to the above-mentioned ~lexibility, be used on all sorts of suitable surfaces as well as under water.
According to the invention construction materials with low speci~ic gravity, pre~erably < 1.3, and with goo~ flexi~i-lity, must be chosen. For the core 11 synthetic fibres with a high ~ensile strength and low elongation may be used, ~or example aromatic polyamide fibres or similar.
The external low-friction protective coating 13 must be re~istant to abrasion and not crack or unravel even at low temperatures. It should preferably consist of a synthetic ela~tomer material such as Hytrel ~.
By optimal choice of suitable materials it has been possible according to the invention to produce cables with a diameter of less than 25 mm, preferably less than 20 mm, with a weight of less than 500 g per meter, preferably under 400 g per meter. A 1500 m long streamer using such a main cable and having 25 m long subsidiary cables with 6 gimbal-mounted equidistant geophones may be towed over a snow/ice surface with a tractive force of _300 kg.
Operative functions The operative funckion is briefly described in the follow-ing. The system is towed by a terrain vehicle. With the dimensions and material specifications given here, and on a snow/ice surface, the tractive force measured by the strain yauge 2 is typically 250-300 kg while in motion and 400-600 kg while starting. A~ter halts of some duration in operations with snowfall and wind, the cable and geophone strings may easily be loosened from the surface by quick .
3~
rounds of inspection using a skidoo or on foot. During movement along straight lines the cable glides smoothly and simply makes tracks in the surface, and the operations are quite unproblematical.
180C turn operations are also quite unproblematical since the chosen materials are n exible even under conditions of extreme temperature. The cable behaves in fact like a flex-ible rope and may be easily coiled and uncoiled.
During operations the detonation unit will normally be ahead of the recording unit and have a fixed distance to the latter. The detonation unit may use:
- surface point charges - surface line charges (detonating cord) - buried charges - mechanical sources (e.g vibrators) The operations may be optimalised with respect to use of resources. As an example one may recommend the following distribution of tasks and crew members when using surface line charges (detonating cord):
Marking 2 persons Supply of explosives from depot 2 persons Emplacement of explosives 2 persons Detonating team 2 persons ~ecording team 2 persons Driver, towing vehicle l person Crew 11 persons Twenty-four hour continous operations (2 shifts of 12 hours) can thus be run with 22 persons in all. The setup is then as follows: First skidoos or tracked Yehicles with personnel for marking, emplacement and detonation. A skidoo is used for transpor~ of ammunition and supplies. Then the towing vehicle, re~ording unit and snow-streamer follow.
Results The system has been tested during exploration on Spits-bergen, Svalbard, where extensive tests and comparisons with conventional setups have also been performed. The tests have given good and reproducible results.
Representative comparisons are made in Figs. 5 and 6 showing conventional setup and snow-streamer respectively. Figures 5 and 6 sh~w stack results obtained in as far as possible identical meteorological conditions (wind-free), source geoflex detonating cord 2 x 50 m (4 kg), shot-point interval 50 m, near-offset 287.5 and with 60 channels in 25 m groups.
It is apparent from Fig. 6 that the streamer results are of high quality and as good as the results obtained by the conventional method as in Fig. 5.
At normal pace and in reasonable terrain 60 shots per hour may be shot using the snow-streamer device, and with the above-mentioned shot pattern 3 km per hour may therefore be covered with a crew of 11 persons.
It can thus be documented that the system functions effici-ently in full-scale operations and that the results are reproducible.
The design shown in Figs. 1-4 represents a preferred oper-ative design only. The design of the snow-streamer itself may be changed within the framework of the invention with respect to length, number of active sections, number of geophone strings and number of geophones.
Furthermore the detonating unit and transport units may be chosen on the basis of current needs and the characteristics of the terrain.
~.
Until now land-based prospecting techniques have been very labour intensive and time-consuming, and have not had the functional or economic efficiency which is at present avail-able for marine seismic surveying.
Several suggestions have therefore been made for improve-ments of land-based seismic operations/ for example the use of a towed main cable (streamer) to which subsidiary cables with automatically adjustable receiving instruments (geophones) are attached at suitable intervals. In order to use such towed systems on a solid surface it has until now been considered important that the cable system be able to withstand severe stresses and be so thick and strong that it can be towed within the area of operation. In snow-and ice-covered regions one has the additional risk that the cable may sink into the snow- and ice-cover and freeze in and thus increasing the strength/stress requirements.
Such a streamer system designed ~or use on snow and ice surfaces is known from US Patent No. 3,954,154 Bedenbender et al. Furthermore a method for mechanised land prospecting using the known streamer is known from US Patent No 3,923,121 Bedenbender et al.
The streamer has a main cable composed of individual sec-tions linked by means of connectors. A number of side strings with individual geophones are connected to the main ' l~a~
cable with the geophones interconnected within the main cable. A tensile core consisting of 7 steel wires is ar-ranged in the central region of the cable in order to with-stand a force of minimum 8 tons (16000 lbs). me steel core alone will thus have a diameter of at least 12 mm, and the resulting cable with surrounding rubber coating, conductor pairs, covering foils and outer mantle will weigh several kilograms per meter and have a substantial diameter of 40-60 mm or more. A streamer using such a cable will be very heavy and can be stiff and unmanageable, like a heavy steel hawser, and is therefore not weel-suited for use in arctic regions. In addition the steel wires will be acoustically active and possibly impair the signal quality. me construc-tions is therefore not suitable for fullscale commercial seismics, and in the above-mentioned patent No., informa-tion is forthcoming on how the streamer concept has behaved in practical trials, or on results achieved.
Thus it is the main object of the invention to develop an easily managed, towable device giving faster and cheaper data collection without adversely affecting the quality of the received signals and giving results as good as or better than those obtainable by conventional techniques.
, It is a further object of the invention to create a streamer which is essentially acoustically inert and does not reduce the quality of the signals recorded by the geophones and receiving instruments.
Yet another object of the invention is to produce a streamer which behaves like a flexible rope, is lightweight and floats upon or glides over the surface with low friction, which is easy to pull and which can serve a large number of geophones. In addition it has the object of preventing the freezing in place of the streamer during halts of some duration and of providing easy re~tarting even if the stre-amer is covered by snow or similar material.
:
3~
These objects are achieved accordiny to the invention by means of an apparatus for seismic exploration to be towed on a land surface and suitable for use on ice/snow surfaces, said apparatus comprising: a towable main cable comprising a plurality of linked cable sections each formed by a core capable of absorbing the stress of towing, at least one layer surrounding said core and formed of insulated conductor pairs of electrically conductive material for the transmission of received signals, and a sheath surrounding and protecting sald at least one layer of conductor 10 pairs, a plurality of geophone strings connected to said main cable at positions spaced longitudinally thereof, each said geophone string having spaced therealong a plurality of geophones electrically connected to said main cable, each said geophone string being capable of being aligned to extend outwardly in varying directions from said main cable with said plurality of geophones of each said geophone string bein~ located at different distances from said main cable; said core and said sheath each being formed of acoustically substantially inert material sufficient to substantially not interfere with seismic signals received by said geophones and transmitted to and by said at least one layer of conductor pairs; and said main cable having an outer diameter of less than 25 mm and a weight of less than 500 g per meter; whereby said main cable wi~h geophone strings connected thereto has a de~ree of flexibility and ease of handling sufficient to enable the same to be wound or coiled in the manner A
3~
26625-g6 of a rope and t~ glide over a ground surface under extreme temperature conditions.
The invention itself will now be described in more detail with references to the attached drawings where:
Fig. 1 shows the end section of the streamer with a towin~ arrangement, Fiy. 2 shows active section~ of the main cable of the streamer with atta~hed subsidiary cables, Fig. 3 shows a cross~section of the main cable, Fig. 4 shows a single auxiliary cable or geophone string, Fig. 5 shows a test line using conventional techniques and ordinary geophones, Fig. 6 shows a corresponding test line using th~
procedure in the invention and employing the streamer.
The main components in the operative device for seismic exploration are a streamer comprising a towing device, active sections and geophone ~trings.
The whole system (Fig. 1) is towed by a terrain vehicle 1 which also contains recording units and associated equipment.
Duriny start and while moving, the tractive force 3a 3~a being used at any time is measured by a strain-gauge 2 and the result shown on a display device in the cabin. Between the strain-gauge 2 and an acoustically inert tow~rope 4 is a safety wire 3 with a breaking strength of about 1.2 tons.
The active sections 6 are pulled by the tow-rope, while the seismic signal~ are transmitted to the recording units by a slack extension cable 5.
The snow-streamer itself (Fig. 2) is a cable 7 consisting of several units or sections - for example 6 units of 250 m. The units are connected by means of quick-release con-nectors 8. A number of auxiliary cables or geophone strings 9 are attached to the cable each carrying a number of re-ceiving instruments or geophones. The geophones are series connected outside the main cabl~, thus reducing the stiff-ness and diameter of the main cable.
The cable 7 is in sections in order to:
- spread the elongation due to stretching during operations ~ver several sections, - facilitate assembly~disassembly, mobilisation/-demobilisation - enable the replacement and repair of defective components while operations are in progress.
The cable 7 (Fig. 3) has at its centre a tension member 11 of acoustically almost inert material which is flexible and of low density, then three layPrs 12 of plastic insu-lated conductor pairs of copper for signal transmission.
The tension member has a diameter of 6.9 mm and a breaking strength of 3000 kg. Kevlar ~ , a synthetic aromatic poly-amide fibre with a specific gravity of 1.15 produced by Du Pont is employed as the fibre material. Externally the cable is covered by low-friction protective coating 13 of elasto-mer material, an acoustically almost inert material with great flexibility and low friction. The main cable has a diameter of 19.2 mm and the weight is 400 g per meter. The .
~L2~ 3~
breaking strenght of the tensile element (core) can there-fore be as low as 3 tons for a 1500 m cable which is to be used in show/ice covered areas. A thin metal coated plastic foil 14 is placed between the conductor pairs 12 and the low-friction protective coating 13.
The low-friction protective coa~ing is coloured off-white in order to avoid the risk that halts of some duration should lead to melting and later refreezing of snow/ice next to the cable. The protective coating has a thickness of 2.6 mm and is guaranteed for temperatures between -51 C and +107~C. It is ~lexible and slips easily over all solid surfaces. The lowfriction protective coating is made of Hytrel ~ a thermoplastic polyester wi~h specific gravity 1.24 produced by Du Pont.
The seismic signals are obtained by means of receiving instruments (geophones~ which are moulded into the auxiliary cables (geophone strings) 9 at fixed intervals (Fig. 4~.
The receiving instruments 10 are series connected outside the main cable so that each geophone string comprises a group (antenna) of for example 25 m length. Each group has 6 or more receiving instruments 10. With an average dis-tance between connecting points of 25 m there are 60 seismic channels on a streamer which is 1500 m long, so that with 6 instruments per group there are 360 instruments. The receiving instruments 10 are hal~-gimballed, that is to say they always lie in a vertical plane coinciding with the direction of the geophone string.
At the points of attachment between the geophone strings 9 and the main cable 7 the breaking strength is 250 kg, while the breaking strength between individual instruments 10 in the geophone strings 9 is 85 kg. These specifications are chosen in order to obtain controlled breaking in the event of jamming of a receiving device 10 in the surface.
~2~
The whole system is waterproof and may be towed as a bottom cable. It is flexible in use and may be towed as one long unit or as several units in freely chosen geometric con-figurations. The system has been tested on ice/snow sur-faces, but can owing to the above-mentioned ~lexibility, be used on all sorts of suitable surfaces as well as under water.
According to the invention construction materials with low speci~ic gravity, pre~erably < 1.3, and with goo~ flexi~i-lity, must be chosen. For the core 11 synthetic fibres with a high ~ensile strength and low elongation may be used, ~or example aromatic polyamide fibres or similar.
The external low-friction protective coating 13 must be re~istant to abrasion and not crack or unravel even at low temperatures. It should preferably consist of a synthetic ela~tomer material such as Hytrel ~.
By optimal choice of suitable materials it has been possible according to the invention to produce cables with a diameter of less than 25 mm, preferably less than 20 mm, with a weight of less than 500 g per meter, preferably under 400 g per meter. A 1500 m long streamer using such a main cable and having 25 m long subsidiary cables with 6 gimbal-mounted equidistant geophones may be towed over a snow/ice surface with a tractive force of _300 kg.
Operative functions The operative funckion is briefly described in the follow-ing. The system is towed by a terrain vehicle. With the dimensions and material specifications given here, and on a snow/ice surface, the tractive force measured by the strain yauge 2 is typically 250-300 kg while in motion and 400-600 kg while starting. A~ter halts of some duration in operations with snowfall and wind, the cable and geophone strings may easily be loosened from the surface by quick .
3~
rounds of inspection using a skidoo or on foot. During movement along straight lines the cable glides smoothly and simply makes tracks in the surface, and the operations are quite unproblematical.
180C turn operations are also quite unproblematical since the chosen materials are n exible even under conditions of extreme temperature. The cable behaves in fact like a flex-ible rope and may be easily coiled and uncoiled.
During operations the detonation unit will normally be ahead of the recording unit and have a fixed distance to the latter. The detonation unit may use:
- surface point charges - surface line charges (detonating cord) - buried charges - mechanical sources (e.g vibrators) The operations may be optimalised with respect to use of resources. As an example one may recommend the following distribution of tasks and crew members when using surface line charges (detonating cord):
Marking 2 persons Supply of explosives from depot 2 persons Emplacement of explosives 2 persons Detonating team 2 persons ~ecording team 2 persons Driver, towing vehicle l person Crew 11 persons Twenty-four hour continous operations (2 shifts of 12 hours) can thus be run with 22 persons in all. The setup is then as follows: First skidoos or tracked Yehicles with personnel for marking, emplacement and detonation. A skidoo is used for transpor~ of ammunition and supplies. Then the towing vehicle, re~ording unit and snow-streamer follow.
Results The system has been tested during exploration on Spits-bergen, Svalbard, where extensive tests and comparisons with conventional setups have also been performed. The tests have given good and reproducible results.
Representative comparisons are made in Figs. 5 and 6 showing conventional setup and snow-streamer respectively. Figures 5 and 6 sh~w stack results obtained in as far as possible identical meteorological conditions (wind-free), source geoflex detonating cord 2 x 50 m (4 kg), shot-point interval 50 m, near-offset 287.5 and with 60 channels in 25 m groups.
It is apparent from Fig. 6 that the streamer results are of high quality and as good as the results obtained by the conventional method as in Fig. 5.
At normal pace and in reasonable terrain 60 shots per hour may be shot using the snow-streamer device, and with the above-mentioned shot pattern 3 km per hour may therefore be covered with a crew of 11 persons.
It can thus be documented that the system functions effici-ently in full-scale operations and that the results are reproducible.
The design shown in Figs. 1-4 represents a preferred oper-ative design only. The design of the snow-streamer itself may be changed within the framework of the invention with respect to length, number of active sections, number of geophone strings and number of geophones.
Furthermore the detonating unit and transport units may be chosen on the basis of current needs and the characteristics of the terrain.
~.
Claims (18)
1. An apparatus for seismic exploration to be towed on a land surface and suitable for use on ice/snow surfaces, said apparatus comprising: a towable main cable comprising a plurality of linked cable sections each formed by a core capable of absorbing the stress of towing, at least one layer surrounding said core and formed of insulated conductor pairs of electrically conductive material for the transmission of received signals, and a sheath surrounding and protecting said at least one layer of conductor pairs, a plurality of geophone strings connected to said main cable at positions spaced longitudinally thereof, each said geophone string having spaced therealong a plurality of geophones electrically connected to said main cable, each said geophone string being capable of being aligned to extend outwardly in varying directions from said main cable with said plurality of geophones of each said geophone string being located at different distances from said main cable; said core and said sheath each being formed of acoustically substantially inert material sufficient to substantially not interfere with seismic signals received by said geophones and transmitted to and by said at least one layer of conductor pairs; and said main cable having an outer diameter of less than 25 mm and a weight of less than 500 g per meter; whereby said main cable with geophone strings connected thereto has a degree of flexibility and ease of handling sufficient to enable the same to be wound or coiled in the manner of a rope and to glide over a ground surface under extreme temperature conditions.
2. An apparatus as claimed in claim 1, wherein said core is formed of a synthetic aromatic polyamide material.
3. An apparatus as claimed in claim 1, wherein aid sheath is formed of a synthetic elastomer material.
4. An apparatus as claimed in claim 3, wherein said synthetic elastomer material comprises a flexible thermoplastic polyester that is resistant to wear and cracking.
5. An apparatus as claimed in claim 1, wherein said sheath is formed of a material having a light color and thereby forming means for preventing ice/snow from freezing about said main cable upon prolonged stoppage of towing thereof.
6. An apparatus as claimed in claim 1, wherein the weight of said main cable is less than 400 g per meter.
7. An apparatus as claimed in claim 1, wherein the outer diameter of said main cable i less than 20 mm.
8. An apparatus as claimed in claim 1, wherein at least one said geophone string has mounted thereon at least three said geophones.
9. An apparatus as claimed in claim 8, wherein each said geophone string has mounted thereon at least three said geophones.
10. An apparatus as claimed in claim 1, wherein at least one said geophone string has mounted thereon at least six said geophones.
11. An apparatus as claimed in claim 10, wherein each said geophone string has mounted thereon at least six said geophones.
12. An apparatus as claimed in claim 11, wherein said geophones of each said geophone string are equidistantly spaced therealong and are gimbal-mounted and the length of each said geophone string is at least 25 meters.
13. An apparatus as claimed in claim 1, further comprising an acoustically inert towing cable connected to said main cable.
14. An apparatus as claimed in claim 13, further comprising a safety wire connected to said towing cable and having a breaking strength less than that of said core of said main cable.
15. An apparatus as claimed in claim 14, further comprising a strain gauge connected to said safety wire for generating an indicia of tractive force applied to said main cable.
16. An apparatus as claimed in claim 1, wherein each said geophone string is connected to said main cable at a point of attachment having a controlled breaking strength, adjacent said geophones in each said geophone string are joined at points of connection having a controlled breaking strength, and said controlled breaking strength of said points of attachment are greater than said controlled breaking strength of said points of connection.
17. An apparatus as claimed in claim 16, wherein said controlled breaking strength of said points of attachment is less than the breaking strength of said core of said main cable.
18. An apparatus as claimed in claim 16, wherein said controlled breaking strength of said points of attachment is approximately 250 kg, and said controlled breaking strength of said points of connection is approximately 85 kg.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO885497A NO165739C (en) | 1988-12-09 | 1988-12-09 | SEISMIC INQUIRY DEVICE. |
| NO885497 | 1988-12-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1294031C true CA1294031C (en) | 1992-01-07 |
Family
ID=19891507
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000611728A Expired - Lifetime CA1294031C (en) | 1988-12-09 | 1989-09-18 | Device for seismic exploration |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4998227A (en) |
| CA (1) | CA1294031C (en) |
| DK (1) | DK174872B1 (en) |
| NO (1) | NO165739C (en) |
| RU (1) | RU2110814C1 (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5274603A (en) * | 1991-07-29 | 1993-12-28 | Shell Oil Company | Marine seismic cable section assembly |
| GB9620391D0 (en) | 1996-09-30 | 1996-11-13 | Geco Prakla Uk Ltd | Land seismic data acquisition method and seismic cable and cable spool vehicle therefor |
| US6061302A (en) * | 1998-07-22 | 2000-05-09 | Western Atlas International, Inc. | Gimbal lock system for seismic sensors |
| US7577060B2 (en) * | 2005-04-08 | 2009-08-18 | Westerngeco L.L.C. | Systems and methods for steering seismic arrays |
| EP2176688A1 (en) * | 2007-08-10 | 2010-04-21 | ExxonMobil Upstream Research Company | Underseas seismic acquisition |
| US9354343B2 (en) | 2009-03-09 | 2016-05-31 | Ion Geophysical Corporation | Declination compensation for seismic survey |
| US8593905B2 (en) * | 2009-03-09 | 2013-11-26 | Ion Geophysical Corporation | Marine seismic surveying in icy or obstructed waters |
| US9389328B2 (en) | 2009-03-09 | 2016-07-12 | Ion Geophysical Corporation | Marine seismic surveying with towed components below water's surface |
| US9535182B2 (en) | 2009-03-09 | 2017-01-03 | Ion Geophysical Corporation | Marine seismic surveying with towed components below water surface |
| US8908470B2 (en) | 2009-11-03 | 2014-12-09 | Westerngeco L.L.C. | Solid seismic streamer cable and method |
| US8792297B2 (en) | 2010-07-02 | 2014-07-29 | Pgs Geophysical As | Methods for gathering marine geophysical data |
| US9423519B2 (en) | 2013-03-14 | 2016-08-23 | Pgs Geophysical As | Automated lateral control of seismic streamers |
| RU2542635C2 (en) * | 2013-07-09 | 2015-02-20 | Виктор Алексеевич Шумилов | Seismic prospecting method |
| US10468158B2 (en) * | 2014-05-07 | 2019-11-05 | Sercel, Inc. | Apparatus and method for an electro-mechanical cable overstress indicator |
| RU2621272C1 (en) * | 2016-04-15 | 2017-06-01 | Российская Федерация, от имени которой выступает ФОНД ПЕРСПЕКТИВНЫХ ИССЛЕДОВАНИЙ | Device for seismic exploration |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2923916A (en) * | 1960-02-02 | woodworth | ||
| US3954154A (en) * | 1970-09-25 | 1976-05-04 | Kruppenbach John A | Towed land cable |
| US3786410A (en) * | 1971-12-27 | 1974-01-15 | Mark Products | Seismic cable assembly |
| US3866162A (en) * | 1973-03-15 | 1975-02-11 | Mark Products | Geophone takeout assembly for seismic cables |
| US4524436A (en) * | 1981-05-15 | 1985-06-18 | Schlumberger Technology Corporation | Pressure wave fiber optic transducer cable |
| WO1983000564A1 (en) * | 1981-08-13 | 1983-02-17 | Carpenter, Allan, Lloyd | Hydrophone cable |
| US4649530A (en) * | 1985-04-19 | 1987-03-10 | Litton Resources Systems | Combination seismic cable |
| US4685090A (en) * | 1985-11-27 | 1987-08-04 | Raychem Corporation | Tubular article |
| US4734891A (en) * | 1986-06-20 | 1988-03-29 | Hughes Aircraft Company | Aft drogue module for towed sonar array |
-
1988
- 1988-12-09 NO NO885497A patent/NO165739C/en unknown
-
1989
- 1989-09-18 CA CA000611728A patent/CA1294031C/en not_active Expired - Lifetime
- 1989-10-23 US US07/425,842 patent/US4998227A/en not_active Expired - Lifetime
- 1989-11-02 RU SU4742260A patent/RU2110814C1/en active
- 1989-12-08 DK DK198906186A patent/DK174872B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| NO165739C (en) | 1991-03-27 |
| US4998227A (en) | 1991-03-05 |
| DK618689D0 (en) | 1989-12-08 |
| NO885497L (en) | 1990-06-11 |
| DK174872B1 (en) | 2004-01-12 |
| NO165739B (en) | 1990-12-17 |
| DK618689A (en) | 1990-06-10 |
| RU2110814C1 (en) | 1998-05-10 |
| NO885497D0 (en) | 1988-12-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |